A gas turbine engine may be used to power various types of vehicles and systems. A particular type of gas turbine engine that may be used to power aircraft is a turbofan gas turbine engine. A turbofan gas turbine engine conventionally includes, for example, five major sections: a fan section, a compressor section, a combustor section, a turbine section, and an exhaust section. The fan section is typically positioned at the front, or “inlet” section of the engine, and includes a fan that induces air from the surrounding environment into the engine and accelerates a fraction of this air toward the compressor section. The remaining fraction of air induced into the fan section is accelerated into and through a bypass plenum and out the exhaust section.
The compressor section raises the pressure of the air it receives from the fan section to a relatively high level. The compressed air from the compressor section then enters the combustor section, where a ring of fuel nozzles injects a steady stream of fuel into a combustion chamber formed between inner and outer liners. The fuel and air mixture is ignited to form combustion gases. The combustion gases then flow into and through the turbine section, thereby causing rotationally mounted turbine blades to rotate and generate energy. The gases exiting the turbine section are exhausted from the engine via the exhaust section.
There is an increasing desire to reduce gaseous pollutant emissions, particularly oxides of nitrogen (NOx), that form during the combustion process. One approach to reduce NOx emissions is the implementation of a rich burn, quick quench, lean burn (RQL) combustion concept. A combustor configured for RQL combustion includes three serially arranged combustion zones: a rich burn zone at the forward end of the combustor, a quench or dilution zone downstream of the rich burn zone, and a lean burn zone downstream of the quench zone. By precisely controlling the zone stoichiometries between the air and fuel, high-temperature excursions can be reduced and the resulting NOx emissions can be minimized. The effectiveness of the RQL concept, however, is primarily dependent on the design of the quench section of the combustor in which the fuel-rich gases from the rich burn zone are rapidly mixed with excess air and passed to the lean burn zone. The design and development of the quench zone geometry is one of the challenges in the successful implementation of low-emissions RQL combustors.
Accordingly, it is desirable to provide a combustor with improved NOx emissions. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.